The present invention relates to methods of forming blister pack packaging.
Articles to be displayed for retail sale are frequently packaged in "blister pack" packaging. A blister pack includes a flat backing sheet, generally of cardboard or plastic, and a plastic "bubble" or "blister", generally of transparent plastic, the backing sheet and blister being joined to form a sealed cavity in which the article rests.
The blister portion of the packaging may be formed by thermoforming a region of a planar plastic material to a desired shape, e.g., by placing the plastic material between a pair of male and female dies that are temperature controlled at a temperature sufficient to soften the plastic and pressing the male and female dies together to form an indentation or "blister" in the plastic.
This process for forming the blister portion is generally effective, but tends to create distortion of the plastic which can be undesirable. In particular, because of this distortion, it is often difficult or impossible to use a plastic material having a decorative graphic pre-printed on it, as the graphic will also be distorted. As a result, any desired graphics are typically applied in a separate processing step, e.g., by applying a decal and/or label to the thermoformed plastic.